Development of New Odor Control Methods

Odor control is one of the rendering industry’s greatest challenges. Research in the early 1970s indicated that untreated rendering plant emissions could be detected up to 20 miles away from rendering plants (Bethea et al. 1973). In-plant control operations for treating high intensity odors using chemical scrubbers, thermal destruction, condensers, and biofilters have advanced odor remediation significantly in the past few decades (Sindt 2006). However, each has drawbacks including energy use and venting of greenhouse gases, storage and use of strong chemical oxidants, and disposal of spent chemical and biological packed bed scrubbers effluent. Also, as urban areas encroach on rendering operations with stringent odor emission regulations, the need for advanced odor protection continues to grow. A number of odor sources other than rendering cookers, such as trucks, could even cause complaints from neighbors.

Clemson University researchers Dr. Daniel Whitehead and Dr. Frank Alexis are collaborating to develop a new, high-tech method of reducing odor emissions. Their cutting edge work involves development of new engineered biodegradable nanoparticles that will destroy malodorous volatile organic odor compounds. These biodegradable nanoparticles are non-toxic to both humans and the environment. This next generation fusion of chemistry and bioengineering is a fresh new approach to the odor remediation problem and offers mechanisms of capturing and destroying odor compounds that have never been explored previously.

Van Langenhove et al. (1982) reported that 110 volatile compounds can be identified in rendering odors, but of those, only 26 contribute most notably to malodorous rendering plant emissions. Those 26 offensive agents include 10 different aldehydes, eight different carboxylic acids, five different sulfur-containing compounds, as well as one alcohol and one amine compound. The majority of these organic compounds are generated from the breakdown of proteins and fats during thermal processing. Other odor compounds of concern from rendering operations include hydrogen sulfide and ammonia. Because of the wide variety of chemical compounds contributing to rendering plant odors, the different chemical structures of these most malodorous agents, and the variability of concentration of these compounds, current strategies for odor control rely on an approach of destroying all emitted volatile compounds. However, it is recognized that the most offensive odor compounds may not be the most prevalent in a mixture of volatiles. Reduction of these compounds could greatly improve malodor problems from rendering facilities. The sensitivity of the human nose can detect and discern chemical odorants at levels as low as 0.1 parts per billion (Van Langenhove et al. 1982, Fazzalari 1973).

Unfortunately, the many valuable contributions the rendering industry makes to society by recycling animal proteins and fats can be quickly dismissed by the public when foul odor releases occur. The rendering industry, therefore, places a high priority on odor control and invests significant resources to combating this on-going problem. Whitehead and Alexis are working in an entirely new direction for odor remediation issues. The work is exploratory and, at this stage, is oriented toward a proof of concept. However, if successful, in the future, a wide variety of odor-capturing nanoparticles could be created and tailored to meet each rendering application need. The goal is to have a nanoparticle spray to distribute in odor problem areas. After the nanoparticles complete their action by destroying the odor compounds, they could be washed down into the wastewater treatment system where they would readily biodegrade.

The term nanotechnology refers to materials that are extremely tiny – on the scale of one to 100 nanometers. A nanometer is one-billionth of a meter. As described on www.nano.gov, a sheet of paper is approximately 100,000 nanometers thick. A strand of human DNA is approximately 2.5 nanometers in diameter. Researchers have learned that nanoparticles on this scale have very unique chemical, physical, and biological properties partly due to their surface to volume ratio. These unique properties allow scientists the ability to use nanoparticles to work on a sub-cellular level. The field of nanotechnology has opened a new realm of research applications in biological and chemical sciences.

Whitehead and Alexis’ work is based on nanoparticle technology that was first developed for medical applications of drug delivery. Therefore, these nanoparticles were developed with rapid biodegradability and toxicological safety considerations in mind (Alexis 2005). In fact, these nanoparticles can be “tuned” to degrade according to a specific pre-determined schedule depending on application and needs. This tunable degradation and non-toxicity make these nanoparticles an excellent environmentally friendly backbone for rendering odor emission remediation.

Whitehead’s laboratory focuses on various aspects of synthetic organic chemistry, including developing new organic reaction methodology, the synthesis of bioactive small molecules, and developing new means of chemical catalysis. By applying fundamental principles of chemical reactivity, nanoparticles will be engineered and fabricated to target the destruction of the most offensive malodorants that cause difficulties in the rendering industry. Their collaborative work is innovative and combines the most recent advancements in synthetic organic chemistry with nanotechnology. Once prepared, the completed nanoparticles will be tested for ability to destroy small odor compounds.

A native of Lexington, SC, Whitehead obtained his bachelor of science and master of science degrees in chemistry from Furman University and his PhD in chemistry from Michigan State University. He was a post-doctoral fellow at North Carolina State University and became an assistant professor at Clemson University in fall 2011.

Alexis obtained his bachelor of science in chemistry, his master of science in materials and interfaces from the Technological University of Montpellier in France, and his PhD in material sciences from Nanyang Technological University in Singapore. Alexis was a post-doctoral fellow of drug and gene delivery at the Institute of Bioengineering and Nanotechnology in Singapore. In 2009, he became assistant professor in the Bioengineering Department at Clemson University.

Alexis began the Clemson University Nanomedicine Laboratory in 2009 where his group works on a variety of nanotechnology applications for drug delivery and tissue engineering. His laboratory team has a multi-prong research thrust including synthesis of new biomaterials and advanced biodegradable polymers. The laboratory is studying the interactions between nanoparticles and biological systems, especially in relation to human and environmental health. Alexis’ team is also developing nanoparticle technologies for in vivo imaging and drug delivery, including targeted cancer therapies.

The rendering odor project will be a proof-of-concept study to demonstrate the reactivity between the engineered nanoparticles and odor compounds. Once the study is completed, the data will help researchers determine whether to conduct further investigations applying the nanoparticles in a rendering plant environment and quantitatively/qualitatively assessing odor reduction. In this preliminary study, the overall goal is to demonstrate an ability to engineer nanoparticles capable of destroying rendering malodor emissions.

The technology proposed in the project represents a new field of study that could open a huge range of applications. For instance, in other future projects to be funded elsewhere, the research team will propose studying use of similar nanoparticle technology for military or environmental applications. In the rendering industry, this technology could augment or possibly even replace existing odor control technologies in the future. The technology could yield cost savings for the rendering industry through reduced energy consumption and reduced emissions of greenhouse gases. Further, this new nanotechnology could feasibly be used not only in the plant and for deodorizing trucks, but also as a non-toxic, biodegradable means to contain odors in a rendering emergency or spill situation.